Onigiri おにぎり
O-nigiri - Rice Ball nigiri/nigiru - grasp/clasp "O" is a prefix to express the respect. Respect and gratitude for the meal, God or farmers. Onigiri may be one of the oldest Japanese sack lunch. When you see a Japanese old film, there must be always some scenes eating onigiri. However the precious white rice were rare, usually it was made with brown rice.
